As world demand for petrochemical products has continued to increase, oil and gas companies have had to expand their exploration and production efforts into developing increasingly deep wells. As a result, the structures constructed to form a well must be capable of operating under larger loads and stresses than ever before. Because failures can have costly consequences, it is important to design all well structures with appropriate safety margins.
One example of such a structure is the well casing. A well casing is a tubular structure generally made of a steel pipe surrounded by a concrete layer that secures the steel pipe to the surrounding formation, thus defining the outside wall of the well. The concrete provides support to the steel pipe, as well as additional isolation layer between the formation and fluids flowing within the casing. In order to determine the correct materials and dimensions for the various casing components, engineers frequently perform computer simulations to model various casing configurations under simulated downhole conditions. The simulations provide the engineer with information regarding the various loads and stresses to which the casing might be subjected, and enable potential designs to be evaluated.
But casing designs are only as good as the underlying simulation model. While simulations of single section casings in vertical wells are generally well understood and produce accurate results, tapered casings, deviated casings and casings with fluid flow restrictions represent indeterminate complex mechanical systems that can be very difficult or impractical to model using existing techniques. While methods do exist wherein these more complex systems are modeled as simpler single-section vertical wells with the results being adjusted to include additional safety margins, such methods can incur a significant risk, given the lack of quantifiable data to support the selected margins.
It should be understood that the drawings and corresponding detailed description do not limit the disclosure, but on the contrary, they provide the foundation for understanding all modifications, equivalents, and alternatives falling within the scope of the appended claims.